In recent years, an image forming device that forms images on a sheet with a decolorable image forming material is known. A decoloring device that decolors images formed of the decolorable image forming material on the sheet by such an image forming device is also known. Some decoloring devices in the related art have a function of reading images to be decolored on the sheet before decoloring the images. However, even when the decoloring device in the related art has a function of saving the images read from the sheet before decoloring, such decoloring device just saves the read images. For example, the decoloring device sometimes performs decoloring processing on a plurality of sheets that are collectively stacked by a user. In such an operation, in many cases, the user stacks a plurality of sheets in any order. In such a case, the decoloring device saves images read from a plurality of sheets in the stacked order. Therefore, even if it is attempted to utilize the images read from the stacked sheets before decoloring, there is a case where it is difficult to utilize the saved images because the saved images may be in any order.